A. Field of the Invention
The present invention relates in general to the design and operation of cotton gins. More specifically, the present invention relates to apparatuses and methods of mechanically separating cotton fibers from foreign matter. Even more specifically, the present invention relates to an apparatus and method of more efficiently separating cotton fibers from foreign matter by utilizing conveying air and gravity separation.
B. Background
Cotton that is harvested from a field consists primarily of the desired cotton fibers and cotton seed and much undesirable foreign matter, such as burrs, sticks, stems and green leaf material. After harvesting, the cotton/foreign matter material is taken to a cotton gin for processing the harvested material into bulk cotton fibers and cotton seed. A large part of a modern cotton ginning plant consists of machines and processes for separating and removing foreign matter from the cotton fiber both prior to and following the actual separation of the cotton lint from the seed (the actual ginning). The machines for removing foreign matter from the seed cotton prior to the ginning are referred to as pre-cleaners. Basically there are two types of pre-cleaners: (1) extractors, which are used for separating the large particles of foreign matter from cotton fibers (for instance, as described in U.S. Pat. Nos. 2,848,635 and 2,862,247 to Vandergriff); and (2) cylinder cleaners, which remove foreign matter that was not removed by the extractor.
Most common extractors make use of cylinders covered with aggressive, hooked teeth. As the cylinders rotate, they engage the cotton fiber/foreign matter mix and drag it over a screening surface. The screening surfaces generally consist of rods or bars mounted laterally adjacent the extractor (toothed) cylinder. The rods or bars are spaced apart a sufficient distance to permit larger particles of foreign matter to separate from the cotton attached to the teeth of the cylinder. The cotton fibers and foreign matter separate centrifugally, which is commonly referred to as a "sling off" process (see U.S. Pat. No. 2,848,635 to Vandergriff). Some cotton will sling off with the foreign matter and this mass of cotton/foreign matter is passed to one or more additional toothed cylinders (i.e., extractors) where the remaining cotton is further mechanically processed and reclaimed from the foreign matter. The cotton which remains engaged by the teeth of the cylinders is doffed by a rotating brush and delivered to the next process.
The process of extracting foreign matter from the seed cotton described above is a multi-stage process. The flow of seed cotton passes through the extractor to be processed by the toothed cylinder where the teeth engage the fibers and slings off the foreign matter. This separates the flow of seed cotton into two streams, one containing good cotton and some foreign matter, the other containing primarily foreign matter and some cotton. Unfortunately, the extraction process is not complete, as not all cotton fibers remain attached to the teeth (some cotton will sling off with the foreign matter) and not all the foreign matter separates from the cotton remaining on the teeth (some foreign matter may follow the cylinder and be doffed with the cotton). The first stream, comprising cotton and some foreign matter that was doffed from the extractor cylinder, generally does not receive further extraction. Instead, it will be passed along for treatment in the cylinder cleaner for further processing to screen out the remaining small trash particles. The second stream, comprising primarily foreign matter and some cotton, will generally pass to one or more additional extractors for further treatment. The cotton from the additional extractor(s) is then joined up with the cotton from the first or prior extractors in the cylinder cleaner. The foreign material separated from the cotton by the extractors is conveyed to a waste disposal system.
To improve the foreign material removal efficiency of extractors, a number of devices have been incorporated into the cleaning process over the years. One of these devices is the use of cylinders, having vanes or blades, that rotate in the opposite direction as the extractor cylinder such that the vanes or blades strip back the foreign material from the cotton. Another device that has been commonly used with extractors is a rotating brush cylinder made up of a cylinder covered with a wire brush material that is used to doff the cotton from the extractor teeth. Also utilized are flexible steel-wire brushes and saws, either singularly or in combination with each other, that separated cotton from the foreign material, generally prior to being treated by the extractor cylinder.
Cylinder cleaners, which are generally used after the extractors described above, primarily consist of cylinders having a number of pins protruding from the surface of the cylinder. The cotton is passed between the cylinders and a screen surface that is configured to facilitate the falling out of the small particles of foreign material remaining in the cotton stream after treatment by the extractor. To improve the efficiency of the cylinder cleaners, the feeder cleaning screens are typically inclined forty to forty-five degrees so that the screen will go higher between the cylinders. Over the years, to improve the separation efficiency of the cylinder cleaners the use of heated air and deflectors have been incorporated.
The devices utilized with extractors and cylinder cleaners to improve efficiency of the mechanical separation of cotton from foreign matter are generally successful in separating most of the cotton and seed from the foreign material. However, the mechanical action of these devices, as well as the extractor itself, tend to lower the grade of the cotton by damaging the spinning value. Lower grade cotton results in lower prices for the cotton produced through the ginning process. As a result, there exists a need for an apparatus that effectively and efficiently separates cotton from foreign material without harming the value of the cotton.